Conventionally, optical connectors for connecting an optical fiber having a circular cross section to a sheet-like optical waveguide have been disclosed. Such optical connectors have a first ferrule and a second ferrule that can be connected to each other with their connecting surfaces abutting against each other. Provided on the insertion surface that is on the side opposite to the connecting surface of the first ferrule is a first receptacle into which an optical fiber is inserted. An optical fiber is inserted into the first receptacle, and the optical fiber whose tip is brought into contact with the bottom of the first receptacle is held by the first receptacle. The second ferrule has a slit-shaped second receptacle that is a hollow extending from the insertion surface on the side opposite to the connecting surface into the body of the second ferrule. A sheet-like optical waveguide is inserted into the second receptacle, and the sheet-like optical waveguide whose tip is brought into contact with the bottom of the second receptacle is held by the second receptacle. The width and the height of the second receptacle are approximately the same as the width and the thickness of the optical waveguide, respectively.
The second ferrule may also have a third receptacle on the connecting surface, and a lens provided at the bottom of the third receptacle. While the first ferrule and the second ferrule are connected, light transmitted over the optical waveguide is collected at the lens, and the collected light enters the center of the optical fiber. A related art example is disclosed in Japanese Laid-open Patent Publication No. 2013-29782.
To hold the optical waveguide inserted into the second receptacle provided to the second ferrule and whose tip is brought into contact with the second receptacle, adhesive or matching oil is used.
A bubble may be formed in the adhesive or the matching oil and stay between the bottom of the second receptacle and the tip of the optical waveguide, and may reduce the optical transmission efficiency at the optical connector.